Field of the Invention
The present invention relates to a pneumatic tire having a tread surface which is sectioned, by a plurality of circumferential grooves extending in a tire circumferential direction, into a center area including a tire equator, a mediate area arranged in an outer side in a tire width direction of the center area, and a shoulder area arranged in an outer side in the tire width direction of the mediate area.
Description of the Related Art
Generally, the tread surface of the pneumatic tire is sectioned into a plurality of blocks by a groove portion such as circumferential grooves extending in a tire circumferential direction and lateral grooves extending so as to intersect the circumferential grooves, and is provided with various tread patterns in accordance with required tire performance and use condition.
The following Patent Document 1 describes a pneumatic tire provided with a tread pattern in which blocks are formed by a number of directional inclined grooves extending in a V-shaped form to the right and left while holding a pattern center therebetween and arranged spaced apart in a tire circumferential direction, and connection grooves connecting the adjacent directional inclined grooves. In this pneumatic tire, in order to solve a problem that wear from a leading side of the block tends to make progress particularly in a shoulder portion by a side force generated during cornering, an excavation is provided in a side wall on the leading side of the block. By providing the excavation in the side wall on the leading side of the block, block rigidity on the leading side becomes smaller, and early wear can be suppressed. However, since the wear on the leading side of the block is suppressed in the pneumatic tire of Patent Document 1, heel-and-toe wear in which the trailing side wears by priority tends to be increased.
The following Patent Document 2 describes a pneumatic tire in which a plurality of circumferential grooves extending along a tire circumferential direction and a plurality of inclined grooves extending from the center in a tire width direction toward an outer side in the tire width diction. In the pneumatic tire, a concave portion is formed in a side wall on the leading side of the second block counting from a shoulder side to a tire equator surface side. As a result, compression rigidity on the leading side of the block is reduced, and it is possible to prevent a pattern noise from being deteriorated in the case where heel-and-toe wear is generated. However, in the pneumatic tire of Patent Document 2, the heel-and-toe wear itself is deteriorated in the same manner as Patent Document 1. Furthermore, since the concave portion is formed along the inclined groove in the entire side wall of the second block, a cross-sectional shape of the inclined groove becomes discontinuous between the second block and the shoulder block, and drainage performance is deteriorated.